For some reason, I can't post the video that BW was referring to (tried three times but I can't get it to go into my Photobucket account and I don't know why) but, on this video, Buddy is not really playing, he is re-directing aggression. He is not being entertained by the action with the cup, he is actually killing the cup and making sure it stays dead. Mind you, not that this action does not work to distract him from other, possibly bad, behavior but distraction is not necessarily entertainment. And I am sorry that you can't see the video because this is, precisely, what I was talking about before. We all tend to anthropomorphize, it's inevitable. We, as humans, see a behavior and our brain, trying to figure out what the bird is doing, looks for a similar occurrence within our experience and assigns it the same meaning but although the bird activity could be almost identical to a human activity, it doesn't necessarily have to have the same purpose. Buddy seems to be playing the way that we would play a game (soccer or rugby, maybe?) but it doesn't have the same purpose for the bird. He is merely hormonal and, as cockatoos get aggressive when hormonal, he is simply acting on the impulse only he is re-directing it toward the cup.
I found a couple of other videos were toos beat up stuff:https://www.youtube.com/watch?v=6u0zQ5VaQEghttps://www.youtube.com/watch?v=iYoc-cRHHMM